If the disk you used is a iscsi/SAN disk

• Backup whole data on the old disk
• Change the disk size in storage size     
• Export the disk to the Linux OS again(usually reboot to recogonize the new size disk)
• After booting, use fdisk to see if the new size has been deteced by OS

# fdisk -l

If yes, then try to boot into rescue mode by installation media

boot> linux rescue

• Try to check if there any filesystem error on current filesystem
• If no, try to increase the partition size by fdisk
• Then increase the filesystem by resize2fs
• Then fsck check filesystem to make sure all filesystem is ok after resize

If the disk you used is a virtual disk in virtual machine

1. Copy method

• Attache new disk to VM
• Partition it and format it
• Create a directory to mount the partition, e.g: There are two partitions in old disk

 /dev/sda1 -> /boot
 /dev/sda2 –> /

Then you had better follow the same organization
    
 # mkdir /newdisk 
 # mkdir /newdisk/boot
 # mount /dev/sdb1 /newdisk/boot
 # mount /dev/sdb2 /newdisk/

• Copy the files from old disk to new disk use either below commands

# cp -ax / /newdisk 
# cp -ax /boot/* /newdisk/boot

[]However, you can use the one partition too, The -a option preserves the original system as much as possible.The -x option limits cp to a single file system; this is necessary to avoid copying the /new-disk and /proc directories.[]

/dev/sdb1 -> /boot
/dev/sdb2 –> /

• Umount all the partition in new disk then use fsck to check if there exist any filesytem error

#fsck.ext3 -f /dev/sdb1 
#fsck.ext3 -f /dev/sdb2

• Mount the /root on new disk again, and change the etc/fstab file to appropriate value

#mount /dev/sdb2 /mnt/newdisk1 
#cd /mnt/newdisk; vi etc/fstab

• Mount the /boot on new disk again, and chagne the boot/grub/grub.conf to ppropriate value

#mount /dev/sdb1 /mnt/newdisk/boot 
#cd /mnt/newdisk/boot; vi grub/grub.conf

• Shutdown the server, remove the old disk
• Try to boot with intallation media and go to rescue mode

boot> linux rescue

Install grub

#chroot /mnt/sysimage 
#cd /boot #grub-install

2. Tar method(it is not suggested, for some bugs may exist there)

• dd method(not suggested if your new disk have different geo parameters than old one)
• Attach a new large file-based file to guest VM as new disk, e.g: /dev/sdb
• Go into run level 1 to shut down the system daemons and preserve the state of the logs, and to prevent users from logging in

#telinit 1

• Try to dd the old disk to new disk

#dd if=/dev/<old disk> of=/dev/<new disk> bs=32256

[]To get better dd performance, here set bs= sector size * sectors * track, you can adjust it based on your disk geo[]

• Shutdown the guest VM
• Remove the old disk configuration from guest VM
• Boot up with installation media
• Go to recure mode

boot> linux rescue 

• Assume the rescue mode detects the installation media and mount it in /mnt/sysimage
• Chroot to /mnt/sysimage

#cd /mnt/sysimage

• Reinstall the grub

 #cd /boot; grub-install <device name> 

• Bootup with gparted cd, and resize the partion
• Resize the filesystem

Reference

• Hard-Disk-Upgrade